The subject matter disclosed herein relates to a machine and a machining method and, more particularly, to a machine for machining or grinding gear teeth and to a gear teeth grinding method.
Gears are used in various industrial and technological applications to permit power transmission from one rotating or translating element to another. Each gear generally includes an array of gear teeth that mesh with the gear teeth of another gear so that the rotation or translation of the first gear can be transmitted to the second. The shapes of the gear teeth can be varied with some gear teeth being linearly shaped, some being helically shaped and others being provided as double-helical or herringbone shaped, and still others being provided as arcuate shaped (or C-Gear) gear teeth.
Gears having gear teeth that are double helically (or herringbone) shaped include a side-to-side (not face to face) combination of two helical gears of opposite hands and, from a top-wise viewpoint, the helical grooves form a V formation with an apex in the middle. Whereas helical gears tend to produce axial loading, a side-thrust of one half of each gear is balanced by that of the other half. This means that gears having double helical or herringbone shaped gear teeth can be used in torque gearboxes without requiring a substantial thrust bearing. Gears having arcuate shaped teeth may also have self-aligning characteristics, which eliminate axial loads with the added benefit of reducing gear tooth end loading due to their inherent ability to adapt to axis misalignment.
However, while these shape gears are desired, due to manufacturing limitations, such gears can only be partially formed. Specifically, current manufacturing techniques use a large grinding wheel which forces a gap to be designed at the apex of the V formation since, when forming one tooth of the V formation, the grinding wheel would otherwise collide with the other tooth of the V formation. Thus, when using a grinding wheel, a true V formation is not formed since a space is required between adjacent teeth to allow for the size of grinding wheel. Further, as these wheels only provide straight line grooves, the resulting teeth are limited to linear shapes. Conversely, while non-wheel precision grinding shapes might allow more complex shapes such as curved lines, these non-wheel shapes do not allow for teeth production at a speed to be economical to create gears in a manufacturing setting. As such, there is a need for a grinding methodology which allows for the creation of gapless double helical/herringbone gear shapes and is sufficiently robust to be used in a manufacturing setting.